Is a thicker rotomolded case always stronger?

Answer: No. Extra gauge adds weight and cycle time, and 4.5 to 6.5 mm with sound ribs covers most duties. Watch the spread between walls and corners instead.

How do I tell a rotomolded case from an injection moulded one?

Answer: Corners and parting line. Rotomolded shells have generous radii, a faint powder texture and no long clamp line; injection bodies show sharp edges and a gate mark.

How often should the gasket be replaced?

Answer: Count openings, not years. Inspect at 800 to 1000 cycles, and every 12 months on coastal sites where rims distort first.

Is there a minimum order for a custom run?

Answer: Yes. A welded tool takes 15 to 25 days, so runs start near 50 to 100 units; colour or insert changes reuse the tool and can fall to about 20.

Can a rotomolded case work at minus 30 C?

Answer: Yes, with the right grade. Linear low density polyethylene stays tough at -40 C if the pin is stainless and the gasket is cold grade silicone.

How to Choose a Rotomolded Case: Five Field Checks

Quick answer: Judge a rotomolded case by five measurable things: wall thickness spread, empty weight against volume, the latch and gasket load path, insert replaceability, and batch weight repeatability.

Five Checks for Rotomolded Case Selection
Wall Thickness, Weight and Mould Temperature
Latches, Gasket and Handle Load Paths
Foam Inserts Specify the Equipment First
Acceptance Data Salt Spray Drop and Stacking
FAQ

1. Five Checks for Rotomolded Case Selection

A rotomolded case is formed by tumbling polyethylene powder on two axes inside a heated mould until it fuses in layers. Thickness comes from powder mass and mould temperature together, not from a single injection shot, so a buyer should measure corners and latch pitch instead of judging finish.

Weight is the most misread signal. An empty 60 litre rotomolded case normally lands between 11 and 14 kg. Under 10 kg, ask where the wall went; over 16 kg, ask whether corners were packed solid for no reason, because that mass is paid back on every carry.

Check	Evidence on the floor	Common misread
Wall evenness	Three points per wall, spread under 0.8 mm	Feeling only the rim
Weight to volume	60 litre empty at 11 to 14 kg	Heavier means stronger
Latch pitch	Two per long side, under 260 mm	Counting latches only
Insert serviceability	Layers lift out whole	Glued grids
Batch spread	Five units, under 2%	Checking unit one

2. Wall Thickness, Weight and Mould Temperature

Wall thickness runs 4.5 to 6.5 mm and thickens to 8 mm at corners and hinge bosses. Each extra 0.5 mm adds about 0.9 kg to a 60 litre case and stretches a 25 minute cycle toward 40.

Rotomolded case in white, lid ajar on a metal rack shelf, two folding side handles, reinforced corner caps, black boxes inside

Mould temperature is held between 200 and 280 C, with the axes alternating a 4 to 1 and a 1 to 1 ratio and powder near 200 mesh. Too cool leaves unfused granules; too hot yellows the interior. A cut section should be dense and even in colour.

Stiffness comes from ribs and radii. Vertical ribs at 90 to 120 mm pitch with 15 mm corner radii let a 4.5 mm wall resist close to a 6 mm flat panel.

3. Latches, Gasket and Handle Load Paths

Sealing is compression, not latch count. A silicone gasket at 50 Shore A, compressed about 30 percent, needs the rim flat within 0.5 mm. Hold 30 kPa for 60 seconds; a drop above 1 kPa means the seal is nominal only.

One latch should hold 300 N for a minute without yielding, and pitch on cases longer than 600 mm should stay under 260 mm or the middle of the lid lifts. Handles take dynamic load: 45 kg static for 10 minutes, with no whitening at the joint. Hinge pins belong in stainless, since a -40 C soak plus 20 cycles exposes plastic ones.

4. Foam Inserts Specify the Equipment First

Measure the equipment outline first, then work back to the cavity: 8 mm of foam on each side, 15 mm at the top, 10 mm at the bottom. Buy the case first and the only fit left is shaved foam, which removes the very margin that absorbs shock.

Divider walls run 8 to 12 mm, with 1.5 mm clearance between compartments and a 5 mm finger gap. EVA at 30 kg per cubic metre suits items under 1 kg; PU at 45 suits items above 3 kg.

5. Acceptance Data Salt Spray Drop and Stacking

Write numbers into the clause. Neutral salt spray for 96 hours covers latch springs, hinge pins and axles, with the shell checked for cracks beyond 2 mm. Drop on six faces from 1.2 m, then stack five high for 24 hours with sink under 3 mm.

Item	Condition	Pass line
Salt spray	96 hours continuous	No red rust, no shell crack
Drop	1.2 m, six faces	No crack, no latch release
Stacking	5 high, 24 hours	Sink under 3 mm
Air tightness	30 kPa, 60 seconds	Drop under 1 kPa

Cycle between -40 C and 60 C for four hours each, three times, then repeat the air and latch tests. That record says more than any brochure.

Conclusion

Five measurements settle most of the decision: thickness spread, empty weight, latch pitch, gasket recovery and batch repeatability. Process consistency, not the sample on the table, sets long term cost, and that is the line a rotomolded case buyer should keep watching.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.